(function(doc, win) {
  var docEl = doc.documentElement;

  var resizeEvt = 'orientationchange' in window ? 'orientationchange' : 'resize';

  var recalc = function() {
    var clientWidth = docEl.clientWidth;

    if (!clientWidth) return;

    docEl.style.fontSize = 50 * (clientWidth / 375) + 'px';
  };

  if (!doc.addEventListener) return;

  win.addEventListener(resizeEvt, recalc, false);

  doc.addEventListener('DOMContentLoaded', recalc, false);
})(document, window);
